Manually displaced and automotive industrial driven by electrical or internal combustion power have been provided heretofore with an upright framework upon which a prong support is vertically displaceable, a pair of prongs forming a fork, projecting forwardly of this carrier to engage beneath a load to permit the same to be lifted on the fork from a stack or from the floor, to be displaced with the vehicle, and to be lowered onto the floor for a stack. In general such loads are so-called palletted loads in which one or more articles are placed upon or secured to a pallet of wood or other material having spaces beneath the load-receiving platform into which the prongs of the fork may extend.
The fork-carrier member is vertically displaceable from a position in which the prongs substantially contact the floor to a relatively high position enabling the apparatus to be used for the stacking of loads to considerable heights.
Such apparatus has been provided heretofore with means for laterally shifting the prongs relative to the upright frame, e.g. when it is desired in lowering the load, to correct the lateral position thereof without maneuvering the entire vehicle.
Such operations are desirable in a large number of cases, e.g. when loads are to be stacked one against another or against a wall toward which the vehicle cannot be more closely maneuvered. The lateral displacement of the prongs is also desirable when the latter are in an elevated position, a lowered position for any intermediate positions to permit insertion of misaligned prongs into the spaces beneath the load-carrying platform.
Furthermore, when a lateral force must be applied to the load after it has been stacked, e.g. to corrent the position of stacked loads, the lateral displaceability of the prongs is of advantage.
Conventional lateral-shift devices for this purpose generally comprise means mounted ahead of the fork-carrier to displace the prongs and hence provide relatively massive structure at a location more forward of the fork carrier, thereby shifting the center of gravity of the vehicle forwardly and disposing the load at a greater distance ahead of the front axle of the vehicle. This has the disadvantage that, together with the increased weight of the lateral-shift device, that the load-carrying capacity of the vehicle is diminished. In many cases, the lateral shift device is hydraulically operable and a connection must be made between the hydraulically driven parts and the remainder of the vehicle by flexible ducts which are susceptible to breakage in the rigorous use to which such vehicles are subject.